1. Field of the Invention
The present invention relates to a vehicle state estimating device, a vehicle control device, and a vehicle state estimating method.
2. Description of the Related Art
A technique of estimating a state amount of a vehicle from a wheel speed has been conventionally reported.
For example, Japanese Patent Application Laid-Open No. H5-319051 discloses a roll detection device for detecting a rotation movement about a front-back axis of a vehicle, the roll detection device including first and second wheel speed detection units for detecting wheel speeds on the left and right of the vehicle, respectively; first and second wheel speed fluctuation amount extracting units for obtaining a fluctuation amount of the wheel speed of a sprung resonance frequency region for each of the left and right wheels based on the detected speeds of the left and right wheels; and a roll computing unit for computing a magnitude of the rotation movement about the front-back axis of the vehicle based on a reverse phase component of the obtained fluctuation amount for the left and right wheels.
In the conventional technique, a transmission property of a sprung unsprung behavior with respect to each input (road surface, steering, accelerator, brake, etc.) is necessary, which transmission property changes by a vehicle state (load state, etc.). Thus, in the conventional technique, when estimating the state amount of the vehicle from the wheel speed, the vehicle property (transmission property of the sprung behavior with respect to the unsprung behavior, etc.) changes by the change in the vehicle state (change in load state, etc.) and thus a highly accurate estimation is difficult. Therefore, improvements still can be made in the conventional technique in enhancing the accuracy of when estimating the state amount of the vehicle from the wheel speed.